Initiator



H. A. LEWIS Sept. 20, 1932.

ZZZ 77 Harold ALewis, luvau'ron INITIATOR Filed April 24, 1931 BY HISATTORNEY Patented 'Sept. 20, 1932' UNITED STATES PATENT OFFICE HAROLD A.LEWIS, OF WOODBURY, NEWJERSEY, ASSIGNOB TO E. I. DU PORT DE NEMOUIRS 8cCOMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELA- WARE INITIATORApplication filed April 24,

This invention relates to initiators for high explosives and moreparticularly to lead azide blasting caps, and comprises a treated steelshell in combination with an explosive charge for the same.

Blasting caps as heretofore manufactured have usually comprised a. shellof gilding metal (copper-zinc), or aluminum, or its alloys. By the termblasting caps as used herein I mean to include either a fuse or ordinarycap, an electric blasting cap, and/or a delay electric blasting cap.Descriptions of each type follow hereinafter. Blasting caps havingmercury fulminate' as the main charge or as a priming agent have usuallybeen constructed of gilding metal, because of the compatibility ofmercury fulminate with such copper alloys. Caps containing lead azidehave usually been made of aluminum or its alloys, since this compound incombination with copper or copper alloys forms supersensitive copperazide, particularly in the presence of moisture and carbon dioxide, thusmaking such combinations hazardous and prohibitive. Furthermore, it hasbeen found that aluminum-shell, lead-azide primed caps give \off anexcessive flash upon detonation, probably because of the combustion ofthe aluminum shell. This flash is frequently sufficient in intensity toignite inflammable gases, such as are present in gaseous coal.

mines, thus making this type of shell also hazardous and prohibitive.

Likewise detonators for high explosive shells and priming cups for smallarms ammunition have commonly been made of gilding metal, of brass, orof copper-nickel alloys. Obviously the cost of shells and other partsmade of these metals has been excessively high.

There are other disadvantages in both aluminum and copper'blasting caps,aside from cost and non-uniformity of form and composition, in that wheneither is used for blasting in the mining of salt, the fine metalparticles that result are generally objectionable in the salt and renderthe salt unsatisfactory for many purposes. For example, when such saltis used in tanning processes, a dis coloration of the hides invariablyresults.

1931. Serial No. 532,471.

Furthermore, when these types of blasting caps are used in connectionwith the blasting of coal, any unexploded caps later present a serioushazard in the subsequent use of the coal. In either case, neither theparticles nor the unexploded caps can be conveniently removed from themined material by the most suitable means, namely, the magnet, becauseof the non-magnetic properties of these metals.

Other metals have been suggested for use in the manufacture of blastingcaps but have not found application because of various disadvantages.

An object of my invention is to provide an initiator that is universallysuitable for all types of firing and blasting operations. A

further object of my invention is to providean initiator, the metallicmaterial of which is compatible with both mercury fulminate and leadazide. Another object of my invention is to provide an initiator whichis constructed of less expensive materials than those heretofore knownand used. ,A still further object of my invention is to provide aninitiator, and particularly a blasting cap,

Other objects will be which is magnetic. apparent as the descriptionproceeds.

Theseobjects are accomplished by the following invention, in which Ihave found that nitrided steel, when used in combination with mercuryfulminate and lead azide, is compatible therewith, yields a product that"is noncorrosive, does not give oif an objectionable flash whenexploded, and has -magnetio properties, besides many other advantages.

The nitrided steel above mentioned is produced by a nitriding process.By the term nitriding as used herein is meant that process in whichsteel is treated at elevated temperatures with substances which give offnitrogen, such, for example, as ammonia. It is believed that in thisprocess an iron nitride is 'thus formed on the surface of the metal. Bythe term steel I mean to include any of the common alloys of iron,containing in small quantities the ordinary impurities commonly foundtherein such as carbon, phosphorous, sulfur, etc, I prefer, however, formy purpose a so-called low carbon steel bewire H carried by the firingFigure 3 represents an electric blasting cap type in which the delayelement cause of the facility with which this material may be deepdrawn. In carrying out the process, a steel shell is formed fromsuitable steel strip, and heated to an elevated temperature, and ammoniais passed over the shell fora sufficient period to produce a surfaceresistant to corrosion. For example, temperatures of 800 to 1,200 F. maybe advanta eously used, and, at these temperatures,

rio s of time varying from one-half to ten ours may be employed. At'these temperatures and time periods, the rate of ammonia passed may besuch that thepercentage of decomposition of the ammoma may vary from 5to 95 per cent, depending upon the surface coating desired.

Upon cooling, a shell is obtained that is very resistant to atmosphericcorrosion, and at the same time has the satisfactory properties whichmake it desirable in a detonator cap or similar combination.Furthermore, I have found that when the steel shell is a'n nealed beforethe nitriding process, its brittleness is reduced, and it isless liableto crack when crimped upon the fuse. Other methods of nitriding thesteel may be used such as Heating the caps or shells in an oven in thepresence of a nitrogen containing material, such for example asguanidine compounds, or other similar compounds.

The nitrided steel shellsdescribed herein may be dyed, lacquered, metalcoated, or metal plated to improve the appearance, or for the purpose ofprotection of the shell, and for this purpose a coating is proposed thatis compatible with the explosive charges incorporatedtherein. Forexample, dyes in solution, lacquers containing nitrocellulose, resins,etc., and coatings or latings of va rious suitable metals are satisactory.

By way of further description and illustration of my invention, I haveshown in the accompanying drawing, in sectional views, three embodimentsthereof applied specifically to blasting caps, in which Figures 1, 2,and 3 represent respectively an ordinary or fuse type blasting cap, anelectric blasting cap, and a delay type electric blasting cap. Figure 4represents a detonator for a high explosive shell, and Figure 5 primingcups suitable for small arms ammunition.

In each of Figures 1, 2 and 3, A represents a nitrided steel shell whichmay be a plain shell or one coated or plated as hereinbefore described.B represents a charge of a secondary detonating material, while 0 repre-Sents a charge of a primary detonating compound, for example, of leadazide.

In Figure 2, E, F, G, and H represent the usual elements of an electricblasting cap in which E is adapted to be fired by the bridge wires G.

af the delay K is substituted for the loose charge E in Figure 2. Whenfired the burning gases from the delay element may escape through theopeningM and may be carried through the outer sleeve N. Figures 4'and 5represent respectively a detonator for a high explosive shell andpriming cups for small arms ammunition of conventional design.

Whereas I have described my invention as applicable particularly toblasting caps, it will be apparent that it may equally well be appliedto primers for ammunition and to detonators for high explosive shellsand drop bombs.

Therefore, by the term initiators, used herein, I mean to includeblasting caps for use with commercial explosives such as dynamite,detonators for high explosive shells, death bombs, hand grenades, andthe like, an primers for small arms ammunition.

It is to be understood that the foregoing examples are illustrative onlyand that other embodiments exist and may be practiced within the'scopeof my invention. For example, nitrited steel shells may be used incombination with other explosive charges such as the series of so-calledstraight-fulminate detonators. It is to be further understood that I donot intend to be limited in my invention except as indicated in thefollowing patent claims.

I claim:

1. An initiator comprising in combination an explosive charge andanitrided steel shell encasing the charge.

2. A blasting cap comprising in combinationan explosive charge and anitrided steel shell encasing the charge.

3. A detonator comprising in combination an explosive charge and anitrided encasing the charge.

4. A priming cup comprising in combinasteel shell tion an explosivecharge and a nitrided steel shell encasing the charge.

5. An initiator comprising in combination a charge of a secondarydetonating compound a charge of a primary detonating compound, and .anitrided steel shell encasing the compounds.

6. A-blasting cap comprising in combination a charge of a secondarydetonating compound, a charge of a primary detonating compound, and anitrided steel shell encasing the compounds.

7. A detonator comprising in combination a charge of a secondarydetonating compound, a charge of a primary detonating compound and thecompounds.

8. A priming'cup comprising in combination a charge of a secondarydetonating compound, a charge of a primary detonating compound and anitrided steel shell encasing the compounds. I

9. An initiator comprising in combination a charge of a secondarydetonating coma nitrided steel shell encasing pound, a charge of leadazide and a nitrided steel shell encasing the compounds.

10. A blasting cap comprising in combination a charge of a secondarydetonating com 5 pound, a charge of lead azide, and a nitrided steelshell encasing the compounds.

'11. A detonator comprisin in combination a charge of a secondarydetonating compound, a charge of lead azide and a nitrided steel shellencasing the compounds.

12. A priming cup comprising in combination a charge of a secondarydetonating compound, a charge of lead azide and a nitrided steel shellencasing the compounds.

13. An initiator comprising in combination a charge of tetryl, achargeof lead azide, and a nitrided steel shell encasing the charges.

14. A blasting cap comprising in combination a charge of tetryl, acharge of lead azide,

and a nitrided steel shell encasing the charges.

15. A detonator comprising in combination. a charge of tetryl, a chargeof lead azide, and a nitrided steel shell encasing the charges.

16. A priming cap comprising in combination a charge of tetryl, a chargeof lead azide, and a nitrided steel shell encasing the charges.

17. An initiator comprising in combination an explosive charge and anannealed, nitrided steel shell encasing the charge.

18. A blasting cap comprising in combination an explosive charge and anannealed, nitrided steel shell encasing the charge.

19. A detonator comprising in combination an explosive charge and anannealed,

nitrided steel shell encasing the charge.

20. A priming cup comprising in combination an explosive charge and anannealed, nitrided steel shell encasing the charge.

21. An initiator comprising in combination 40 an explosive charge and anitrided, coated,

steel shell encasing the charge.

22. A blasting cap comprising in combination an explosive charge and anitrided, coated, steel shell encasing the charge.

23. A detonator comprising in combination an explosive charge and anitrided, coated, steel shell encasing the charge.

24. A priming cup comprising in combination an explosive charge and anitrided, coated, steel shell encasing the charge.

- 25. An initiator comprising in combination a charge of lead azide, anda nitrided steel shell encasing the charge.

In testimony whereof, I aflix my signature.

HAROLD A. LEWIS.

